Tow cutting apparatus having knife resharpening means



Oct. 14, 1969 JAMES w. u. HIEIJNIS TOW CUTTING APPARATUS HAVING KNIFE RBSHARPENING InLANS 3 Sheets-Sheei 1 Filed Jan. 11, 1967 6 8 H D 4 4 RM T E T PM I ML WA IIIIIVIIII RU ML U o A0 v N I RT 0 R 0 O 4 O N S 2 a 4 R O I 5 PC M v v m A m 06L 1969 JAMES w. u. HEIJNIS 3,472,107

TOW CUTTING APPARATUS HAVING KNIFE RESHARPENING MEANS Filed Jan. 11, 1967 3 Sheets-Sheet f.

Och 1969 JAMES w. u. HEIJNIS 3,

TOW CUTTING APPARATUS HAVING KNIFE RESHARPENTNG MEANS Filed Jan. 11, 1967 3 Sheets-Sheet United States Patent Office,

3,472,107 Patented Oct. 14, 1969 U.S. CI. 83-71 4 Claims ABSTRACT OF THE DISCLOSURE Knives helically positioned upon a rotating cutter head cut tow clamped between teeth of cooperating draw wheels. An adjustably positioned grinding member periodically resharpens the knives to increase operating efficiency and to improve the quality of the cut fiber.

BACKGROUND OF THE INVENTION The present invention relates to apparatus for cutting tow into staple fibers.

In a known apparatus of the above described type the knives may pass between the nipping teeth of two draw wheels while severing the tow clamped by and passed between said draw wheels, the clamping faces of the teeth of one of the draw wheels being on a flat surface and the clamping faces of the relatively small number of teeth'of the other draw wheel being on a conical surface which rolls in true contact with the flat surface of the first wheel, By a suitable arrangement of the cutter head relative to the draw wheels, that is with the shaft of the cutter head parallel to the plane through the shafts of the draw wheels, crossing the shaft of the flat wheel at an angle of 45, it is possible for the knives to be moved along with the tow in the direction of travel with the movements of the knives relative to the tow having a chopping as well as a cutting component. These components are of approximately the same magnitude, and the knives, which move through their own planes, hit the tow with their edges across the full width of the tow section thereby severing the tow clamped between two successive pairs of teeth.

It has been found that in this way a maximum edge life of the knives may be obtained and that, moreover, the cutting energy remains limited to a minimum. As is known, by the edge life of a knife is to be understood the number of cuts made by the knife before the quality of the fibre begins to decline appreciably. This loss of quality is particularly noticeable by irregular or fused fibre ends, which give rise to difficulties in the further processing thereof. A longer edge life has been recognized as advantageous by those skilled in the art. Thus, the art has recognized that the edge life of the knives may be prolonged by regrinding the knives during cutting. A known embodiment of such an apparatus utilizes a knife in the form of a screw blade. The screw blade rotates between the teeth of two rotating cylindrical draw wheels. The screw blade is sharpened by an abrasive stone which is reciprocated parallel to the shaft of the screw blade in contact with the knife edges. However, this apparatus sufiers from drawbacks since it is difiicult and costly to accurately manufacture such screw blades. Furthermore, the move-ment of the screw blade relative to the tow does not have a chopping as well as a cutting component. Also, as a result of inaccuracies shape inherent in such a configuration of the knife, the grinding or sharpening is not always satisfactory. Parts of this type of knife will still become blunt or show burrs in a relatively short time.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an improved tow cutting apparatus which substantially overcomes the aforementioned disadvantages of prior art construction.

In accordance with the present invention, tow cutting apparatus having a rotatable cutter head with a plurality of knives mounted in the rim thereof is utilized in combination with a rotatable grinding disc which is positioned facing the hyperboloid surface which is generated by the path of the knife edges. The grinding disc, which is adjustably positioned, is coupled to an actuating system which may move the disc along a straight generatrix of said hyperboloid surface. As a result of the particularshape of the cutter head and the special way in which the grinding disc traverses the path of the knife edges, it is possible to sharpen the knives with a high degree of accuracy using relatively simple means. The knives' may have a simple shape, and the grinding disc may be of a conventional type. Moreover, there is no need for a complex synchronization of the movement of the cutter head and the knife grinding means as is the case with the known apparatus utilizing a screw blade shaped knife. The present invention has the further advantage that the grinding disc may be moved out of contact with the knives in a simple way by periodically lengthening the traverse stroke of the grinding disc so that it is moved beyond the tips of the knives. This procedure avoids grinding the knives continuously so that the knives are not ground longer than is necessary to keep them sharp.

Due to wear of the grinding disc, the edge life of the knives may be limited by the decreasing grinding action of a worn grinding disc. In accordance with the present invention, this limiting factor on the edge life of the knives may be obviated by providing a diamond point or similar means for reconditioning the grinding disc when necessary.

The above and other objects, features and advantages of the invention will become more apparent as this description proceeds.

BRIEF DESCRIPTION OF THE DRAWING FIGURE 1 is a plan view of one embodiment of a tow cutting apparatus constructed in accordance with the present invention, with the means for regulating the grinding disc being shown somewhat diagrammatically.

FIGURE 2 is a front elevational view of the FIGURE 1 embodiment omitting the grinding disc and associated control means.

FIGURE 3 is a partial cross-sectional view on an enlarged scale showing the position of a knife with respect to the cooperating teeth of the draw rollers.

FIGURE 4 is a partial plan view on an enlarged scale showing details of the connection of a knife to the cutter head and further illustrating the relationship of a knife to the tow to be cut.

FIGURE 5 is a partial vertical cross-sectional view taken on the line 55 of FIGURE 4.

FIGURE 6 is a somewhat diagrammatic view illustrating the movement of the grinding disc.

DETAILED DESCRIPTION Referring now to the drawing, and more particularly to FIGURE 1, there is illustrated a preferred embodiment of the present invention which includes a pair of cooperating draw wheels 1 and 2. The larger draw wheel 1 is rotated by a shaft 3 which is supported in bearings 5 and 6. The smaller draw wheel 2 has a conical ci1'- cumferential rim and is rotated by a shaft 4 which is supported in bearings 7 and 8. The shafts 3 and 4 lie in the same horizontal plane so that the conical rim of the draw wheel 2 can rotate about its axis while coming into true contact with the surface of draw wheel 1. The draw wheels 1 and 2 are provided at their circumferential rims with teeth 9 and 10 respectively. The number of teeth 9 of the larger draw wheel is a multiple of the number of teeth 10 of th draw wheel 2. As is clearly shown, the teeth 10 are provided in the conical rim so that the teeth 9 and 10 which have the same pitch come into rolling contact to clamp the tow, but do not intermesh.

A gear rim 11 which is splined to the shaft 3 of the draw wheel 1 and a cooperating conical gear 12 on the shaft 4 of the draw wheel 2 ensure that the circumferential speeds of the draw wheels are equal.

A cutter head 13 is rotated by a shaft 14 which is supported in bearings 15 and 16. The shaft 14 is parallel to the plane containing shafts 3 and 4, and shaft 14 crosses shaft 3 at an angle of 45. By means of a gear wheel transmission (not shown) the shaft 14 can also be coupled to the shaft 3; see Patent No. 3,150,552 dated Sept. 29, 1964. A plurality of knives 17 equal in number to the number of teeth 10 of draw wheel 2 are mounted in the rim of the cutter head 13. The knives are positioned about shaft 14 at a helix angle of about 45". When the path of a knife 17 coincides with the tangent line between teeth 9 and 10, the cutting edge of the knife coincides with the tangent line, and the knife lies in the plane through the shafts 3 and 4.

As shown in FIGURES 2 and 4, a tow is drawn between the draw wheels 1 and 2 to be cut into staple fiber which falls down in the form of tufts (not shown). A typical tow may be, for example, a 250,000 denier tow composed of filaments each having a 1.5 denier.

Referring now to FIGURE 3, the tow is clamped between resilient gripping surfaces 18 and 19 which are secured to the teeth 9 and 10 respectively. The gripping surfaces are made of rubber or similar material. This figure illustrates the position of a knife 17 relative to the teeth 9 and 10 at the moment the tow is about to be cut. The dash lines indicate subsequent positions of the knife.

The spatial relationship of a knife 17 with respect to the tow to be cut is further evident from FIGURE 4 which also illustrates the mounting of a knife 17 in the cutter head 13. Each knife is positioned within a knife holder 22 which extends into a channel 32 provided in the cutter head 13. The holder 22 is dovetailed to fit between a clamping block 23 and an abutment 21. A bolt 24 and an associated washer 33 are located in a bore 25 with the bolt extending through a counterbore in abutment 21 into threaded engagement with the clamping block 23. By loosening bolt 24, the position of the knife holder may be adjusted.

A grinding disc 26 is utilized to resharpen the knives 17. As shown in FIGURE 1, the grinding disc is positioned at an angular dstance of about 90 from the point relative to the cutter head where the two draw wheels contact each other. The grinding disc 26 is so positioned that its working surface makes an angle of a few degrees with the surface of the knife being resharpened. As a result, at any given time, only one side of the grinding disc will be in contact with a knife. A motor 27 which is employed to rotate the grinding disc is mounted on a slidable support 28 which may be reciprocated along a guide 29 essentially parallel to shaft 14. The guide 29 is positioned essentially parallel to the edge of a knife which is being resharpened by the grinding disc. Thus, guide 29 is parallel to the generatrix of the hyperboloid surface generated by the movement of the edges of knives 17 so that the point of contact between the grinding disc and the knives is traversed along said generatrix.

When the knives are being resharpened, the grinding disc 26, in addition to its rotary movement about its axis, makes a traversing movement over a distance which corresponds to the length of the knife edge. After a predetermined grinding period, the support 28 is moved within guide 29 to a position in which the grinding disc 26 no longer contacts the knives 17.

The position of guide 29 within a support 56 may be adjusted in any known manner, for example, by means of bolts passing through slots in the walls of guide 29 and support 56. After the knives have been ground several times, the position of guide 29 may be adjusted to compensate for disc and knife wear.

The actuating means for the grinding disc 26 and associated structure will now be described with reference to FIGURE 1. Suitable control means such as a r.p.m. counter 42 is operatively connected to a motor 40 driving shaft 3 to sense the number of revolutions of shaft 3. This signal is fed to a programmed controller 44 which is operatively connected to a transmission 46 associated with the drive motor of shaft 3. When shaft 3 and hence cutter head 13 have made a predetermined number of revolutions, usually between 1,000 and 10,000 and preferably about 2500 revolutions, the programmed controller operatively connects a grinder actuator 48 to the motor driving shaft 3 via the transmission. Suitable linkages 50 and 52 connect the transmission to the motor 40 and grinder actuator 48, respectively. The grinder actuator 48 thereupon moves the grinding disc 26 from an inoperative position to an operative position in which it may traverse the blades of knives 17 by means of a suitable mechanical linkage 54. At the same time, the programmed controller actuates motor 27 to rotate the grinding disc. After a predetermined period of time sufficient to resharpen knives 17, support 28 which carries the grinding disc 26 is moved within guide 29 away from knives 17 to the inoperative position.

The details of a suitable controller and a suitable actuator are not part of this invention and are known to those skilled in the art.

As shown in FIG. 1, a diamond point 30 which is adjustably positioned in a support 58 is located in line with the knives 17 on the generatrix of the hyperboloid surface generated by the point of contact of the knives and the grinding disc 26. After a number of grinding or resharpening operations which cause wear of the grinding disc 26, the support 28 is moved further away from the knives so that the grinding disc is moved into contact with the diamond point 30 to be reconditioned. This further movement to accomplish reconditioning is also carried out through the agency of the programmed controller and the grinder actuator. By suitably adjusting the program of the controller to the nature of the tow to be cut, the hardness of the knives, etc., the cutting apparatus may be kept in operation for long periods of time, for example, 1,000 to 2,000 hours. In this way, the time lost in exchanging worn knives is reduced to a minimum, and the risk of considerable variations in the shape of the cut staple fibers is minimized.

FIGURE 6 schematically indicates the various positions of the grinding disc 26 relative to a knife 17. From this figure, it is evident that the grinding disc 26 moves parallel to the direction of the edge of knife 17 when the latter is in contact with the grinding disc. As seen from the various positions of the grinding disc indicated by dash lines, the grinding disc 26 may be moved into position with the diamond point 30 to be reconditioned, may be moved into an inoperative position between diamond point 30 and the path of knives 17, and may traverse the edge of the knives to an extreme left position opposite the bottom 31 of the knife edge.

I claim:

1. In a tow cutting apparatus comprising a pair of cooperating draw wheels having teeth to clamp tow to be cut, a rotatable cutter head positioned in operative relationship with respect to said draw wheels and having a plurality of knives mounted on its rim for cutting said tow, a shaft for rotating said cutter head, said knives being helically positioned about the shaft of said cutter head, the improvement comprising rotatable grinding means positioned facing a hyperboloid surface generated by the path of the edges of said knives, control means to move said grinding means from an inoperative position to an operative position once for each 1,00010,000 revolutions of said cutter head for resharpening the edges of said knives, and actuator means to insure movement of said grinding means in operative position along a straight generatrix of said hyperboloid surface.

2. Apparatus according to claim 1 wherein said actuator means causes said grinding means to be reciprocated along the edges of said knives once in each grinding cycle.

3. Apparatus according to claim 1 and further comprising means for reconditioning said grinding means, and additional control means to periodically move said grinding means into contact with the reconditioning means.

4. In a tow cutting apparatus comprising a pair of cooperating draw wheels having teeth to clamp tow to be cut, a rotatable cutter head positioned in operative relationship with respect to said draw Wheels and having a plurality of knives mounted on its rim for cutting said tow, a shaft for rotating said cutter head, said knives being helically positioned about the shaft of said cutter head, the improvement comprising rotatable grinding means positioned facing a hyperboloid surface generated by the path of the edges of said knives, a slide support, a

motor mounted on said support for rotating said grinding means, a guide in which said support may reciprocate, control means including a programmed controller to pcriodically move said grinding means from an inoperative position to an operative position for resharpening the edges of said knives, actuator means to move said support and said grinding means in its operative position parallel to the generatrix of the surface generated by the path of the edges of said knives, a drive shaft for rotating at least one of said draw Wheels, and means operatively connected to said programmed controller to sense the number of revolutions of said drive shaft.

References Cited UNITED STATES PATENTS 2,305,312 12/1942 Kern. 3,150,552 9/1964 Heijnis 83-913 X 3,374,699 3/1968 Schmermund 83174 ANDREW R. JUHASZ, Primary Examiner J. F. COAN, Assistant Examiner US. Cl. X.R. 

